1. Field of the Invention
The present invention relates to a method for improving the adhering ability of the surface of vulcanized rubber.
2. Description of the Prior Art
It is generally difficult to adhere a vulcanized rubber to the other materials and such an adhering is more difficult than the case when an unvulcanized rubber is superposed on or contacted with the other materials and vulcanized and simultaneously adhered.
As a method for adhering a vulcanized rubber, it has been proposed that the surface of the vulcanized rubber is applied with a solution of a unvulcanized rubber in an organic solvent, such as toluene and the like, that is a rubber cement and dried, after which the thus treated vulcanized rubber and an unvulcanized rubber are superposed and pressed and vulcanized to ahdere the unvulcanized rubber to the vulcanized rubber. However, there is a defect that a mold corresponding to the requirement in an integrating molding must be manufactured in every molding and further a complicated mechanical apparatus is necessary for the pressing and heating. Furthermore, the object to be adhered is limited to the same kind of unvulcanized rubber.
As the other method, there has been proposed that a rubber cement obtained by dissolving unvulcanized polychloroprene (CR), acrylonitrile-butadiene coplymeric rubber (NBR), generally referred to as "nitrile rubber," a graft copolymeric rubber obtained by grafting a vinyl compound, such as methyl methacrylate and the like to the above described rubbers or blends of these rubbers with phenolic resins, in an organic solvent, is used for adhering the vulcanized rubber to the other materials, but this method cannot provide a satisfactory adhesion.
Moreover, there has been a process wherein a spontaneous vulcanizing rubber cement which vulcanizes at room temperature by using vulcanizing superaccelerators or sulfur chloride, is used, but this process also cannot provide a satisfactory adhesion.
As a surface treating process of a vulcanized rubber which has been heretofore carried out, there has been proposed that the surface of the vulcanized rubber is strongly oxidized with concentrated sulfuric acid, potassium permanganate, potassium dichromate and the like and washed with water to remove the above described treating agent and then the vulcanized rubber is bent to form fine cracks on the whole surface, thereafter the thus treated vulcanized rubber is applied with an adhesive and then adhered to the other materials.
However, the user of these strong acids or strong oxidizing agents must pay a full attention in the handling. Nevertheless, the adhesion is not satisfactory and the vicinity of the surface of the vulcanized rubber is deteriorated by such strong oxidizing agents.
In addition, it has been well known that the surface of a vulcanized rubber is treated with a solution of an organic polyisocyanate compound, for example, triphenylmethane triisocyanate solution (made by Bayer, Germany, Desmodur R (Trade Mark)) but this process was not possible to provide a satisfactory adhesion.
The present invention enables one to adhere strongly vulcanized rubbers mutually or a vulcanized rubber to the other various materials by using an ahdesive or without using an adhesive by treating the vulcanized rubber surface with a solution of iodine isocyanate or a mixed solution of iodine isocyanate and iodine to provide a high adhering ability on said surface and then contacting the thus treated vulcanized rubber with a vulcanized rubber or the other materials to be adhered tightly and pressing and heating them.
The method for improving the adhering ability of a vulcanized rubber surface according to the present invention can be effectively utilized particularly in the following fields;
a. composite materials, in which vulcanized rubber particles are dispersed and embedded in a matrix, PA1 b. a method for retreading pneumatic tires, PA1 c. pneumatic safety tires in which the bead portion and the bead seat of the rim are integrated, PA1 e. a dock fender wherein a synthetic resin layer is integrally formed to an impact receiving portion. PA1 a. composite materials having a satisfactory bending fatigue resistance in which vulcanized rubber particles are dispersed and embedded in a matrix, PA1 b. a method for retreading pneumatic tires by which any vulcanization step for adhering is omitted and the retreated pneumatic tires having a high durability can be obtained, PA1 c. a safety tire in which the bead portion of pneumatic tire and the bead seat in the rim are strongly and simply integrated, PA1 d. a method for partially repairing tires in which the repairing operation is easy and can be effected in a short time and further a high durability is obtained and the performance of the retreated tire is not lowered by the repairing, and PA1 e. a dock fender in which a synthetic resin layer is strongly integrated with the dock fender body composed of the vulcanized rubber. Furthermore, the present invention can be applied broadly to industrial articles, for example, endless workings of conveyor belts and rubber crawlers and the method of the present invention can be effectively used for molding of articles, in which the vulcanized rubber is a constituting element. PA1 a. composite materials in which the vulcanized rubber particles are dispersed and embedded in a matrix composed of castable polymers, PA1 b. a method for retreading the pneumatic tires, PA1 c. a pneumatic safety tire in which the bead portion and the bead seat are integrated, PA1 e. dock fenders in which a synthetic resin layer and the impact receiving portion are integrated and the like, the present invention have solved various problems which have been encountered because of the low adhering ability of the vulcanized rubber, and can accomplish the above described objects (a)-(e). Therefore, the present invention has very high commercial merits.
d. a method for partially repairing pneumatic tires, and
A. It has been already known that vulcanized rubber particles can be dispersed in a castable polymer, for example, polyurethane elastomer. However, the inventors have found that the composite material produced by the conventional process has great defects. Namely, when a stress is periodically applied to such composite materials, a satisfactory bending fatigue resistance cannot be obtained. The composite material produced by the conventional process in which black vulcanized rubber particles compounded with carbon are dispersed in a colorless and transparent polyurethane elastomer matrix, is generally seen black but when this composite material is bent and the bent surface is observed, it is found that the maximum bent portion, that is, only a zone where the stress has most concentrated, is seen to be white so that said portion floats. This is because numerous fine breakages are formed inside the portion where the stress concentrates.
B. As the method for retreading pneumatic tires, it has been known that a vulcanized tread rubber is wholly or partially fixed to a base tire to be retreaded. The prior such type method is as follows as shown in U.S. Pat. No. 2,976,910.
A tread rubber layer of tire run for a given distance is carefully removed and said tire is subjected to a buffing and then on the resulting base tire, a vulcanized or semi-vulcanized tread rubber layer having a tread pattern is forcedly contacted through an unvulcanized rubber sheet and then the assembly is pressed and heated, whereby the vulcanization and adhering are effected. Even if this method has made various improvements as compared with the conventional methods for retreading tires, there are the following defects.
That is, since the vulcanization step is necessary, the installation therefor is necessary.
By selecting the quality of the rubber to be inserted between the base tire and said vulcanized tread rubber layer, a certain variation may be made but the heating is essential for the vulcanization and this heating brings about the heat deterioration of the base tire. For solving this defect, the vulcanization at a low temperature for a long time has been proposed but this means lowers the production efficiency and particularly in the spontaneous vulcanizing rubber the adhesion is defficient. In addition, in the use of an adhesive, the defficiency of the adhesive has never been solved.
C. The pneumatic tire has the following skeleton struture. A pair of bead wires having ring forms composed of non-elongating metal wires are provided at a space in the axial direction of tire and carcass plies in which the cords composed of fibers, such as textile, metal or glass are covered with a rubber, are held and secured in a toroidal form aside from one bead wire to another bead wire.
Such a pneumatic tire is set to a rim in the following manner. A bead seat of the rim mounts the bead portion housing the above described head wire and supports the whole tire and air is filled in the inside of the tire and the inner pressure of the filled air compresses the bead portion to the bead seat of the rim which inclines at a given angle against the axial direction of tire and the rim flange which limits the outer periphery of the bead seat.
This compressing force is strong and therefore, of course, when the tires run straightly and even when the running direction of tires is curved and the tires are subjected to the force of the axial direction of tires (referred to as "side force" hereinafter), if said force is mild, the bead portion neither separates nor gets out from the bead seat of the rim.
However, when the car speed is high over a certain degree, if a particularly large side force is applied as when the tires are rapidly curved, the side force becomes larger than the compressing force owing to the inner pressure and the bead portion separates or may get out from the bead seat. When a tube is used in the inner portion of the tire, the unstability of the handle and the cutting of the tube only occur. However, in the tubeless tire recently broadly used in view of safety against puncture, which is caused, for example, by stepping on a nail, in which a rubber sheet having a given thickness is adhered to the inner surface of the tire and a tube is omitted, said tire and the rim are directly sealed at the bead portion, so that as soon as the bead portion is separated from the rim flange in the manner as described above, the inner pressure is rapidly exhausted and such a case is very dangerous.
Therefore, the tire designers have attempted to make the compression of the bead wire to the rim fully strong but if such a means is adopted, it is very difficult to set the tire into the rim.
On the other hand, in such a type tire that the tire and the rim are integrated by the inner pressure in this manner, if the inner pressure is exhausted or decreased owing to any cause, the tire separates from the rim and gets out from the rim and the running becomes impossible or if this phenomenon occurs suddenly, there is a possibility of occurrence of a great accident.
Heretofore, various attempts have been made for solving this problem.
For example, Japanese laid open Pat. application No. 4,552/71 and U.S. Pat. No. 3,669,174 disclose that the bead portion is mechanically fixed from the inside and outside of the tire.
Alternatively, West Germany laid open Pat. application No. 2,055,172 discloses that the rim and the tire are pressed and heated to effect vulcanization and adhering.
In the former process, the cost of the rim raises and further when the inner spacer and the outer spacer are bound by bolts and the like, the airtight sealing process is complicated and this process is not reliable.
In the latter process, the surface treatment of the rim and the large size apparatus are necessary and this process cannot be simply effected. A simple and effective method for adhering the tire to the rim, by which the defects of these prior technics, can be obviated and the pneumatic tires and rims are strongly and simply integrated, so that when the tires run on road in normal state, even if a greatly large side force occurs, the tires neither separate nor get out from the rims, and further even if the inner pressure of the tires decreases or in an extreme case, is exhausted, the tires do not get out from the rims and can run safely and in which, if necessary, the tires can be removed from the rims relatively easily, has been demanded.
D. Some methods for partially repairing tires have been known. In these methods, when a damaged hole which perforates from the tread rubber layer to the carcass layer (rubber applied cord cloth layer), is caused by a sharp rock or metal piece and the like, muddy soils and the like around the damaged portion are removed by washing and then a rubber is embedded into the damaged hole and said portion is partially pressed and heated to effect a partial vulcanization or said portion is embedded with a spontaneous vulcanizing rubber in order to omit the vulcanization step.
However, the tire to be repaired is composed of a vulcanized rubber and as well known, the vulcanized rubber has many difficulties in the adhering and therefore the circumference of the damaged hole must be previously subjected to buffing, applied with a rubber cement (a solution of unvulcanized rubber dissolved in an organic solvent, such as gasoline) and then fully dried, after which the thus treated damaged hole is embedded with a rubber. Accordingly, this method is very troublesome and nevertheless the adhesion is low and the complete repairing cannot be made.
E. It has been already known that synthetic resins, such as polyurethane resins, epoxy resins, polyethylene resins and the like are adhered to the surface of an impact receiving portion of a dock fender composed of a vulcanized rubber to protect the rubber body from abrasion and impact due to the impact of ships. However, the adhesion of the synthetic resins to the rubber is poor, so that the synthetic resins are readily separated and dropped off due to the difference of elastic strain and satisfactory dock fender has never been obtained.
The object of the present invention is to solve the above described various problems which are caused because of the low adhesion of the vulcanized rubber, by providing a high adhering ability to the surface of the vulcanized rubber in order to obtain a strong adhesion between mutual vulcanized rubbers or between a vulcanized rubber and the other various materials and to provide,